For accurate manufacture of corrugated products, a machine must have a systematic and meticulous material handling apparatus. This handling apparatus must supply a reliable and consistent flow of material to the corrugating machine.
The manufacture of corrugated metal strips entails a feeding of metal ribbon web from a coil to a series of forming rolls. Typical apparatus for use in Such manufacture is shown, for example, in U.S. Pat. Nos. 3,998,600, 4,067,219, 4,262,568, and 4,507,948. Typically the ribbon web is dispensed from a coil by pinch rollers or the like. Coil inertia and drag during start-up adversely affect control of the fin height of the finished product. Moreover, such inertia and drag vary as coil diameter decreases. In the event of a machine shut-down, coil momentum continues to unwind ribbon web.
Generally, a dancer arm is pivoted to the handling apparatus and has a weighted roller on its free end to contact the metal ribbon web to take up the slack from coil momentum. The dancer arm provides a signal to a controller for varying the speed of the coil drive motor which controls the feed rolls and acts as an accumulator of the metal ribbon web before introduction into the form rolls of the machine.
Typically, a dancer arm has a fixed pivot and travels in a uniform arc. A dancer arm at the mid-point of its arc or normal position signifies that the metal stock is travelling a speed equal to the normal operating speed of the fin rolling machine. When the dancer arm is at the bottom of its arc or the low position, the coil drive motor speed is too fast causing slack in the metal ribbon web. If the dancer arm is in its high position, the coil drive motor is too slow and therefore not providing enough metal ribbon web to the machine and causing excessive tension on the metal web.
When the dancer arm is not in the normal position, a signal is sent to the controller to accelerate or decelerate the coil drive speed. As the arc of movement of the dancer arm moves away from a neutral position, the magnitude of the signal increases for each increment of movement of the dancer arm. Thus, if the coil drive motor is accelerated, the metal ribbon web may be fed too fast, thereby causing slack in the metal ribbon web. If the dancer arm, with its weight on the end, swings to the low position with a force equal to the weight times the distance from the pivot point, excess force may be provided on the metal web and may result in breakage of the metal ribbon web.
Also in such prior arrangements, three motors are required and necessitate a sophisticated control system to synchronize the speeds of a coil drive motor, a machine drive motor and a web handling drive motor.
Among the objectives of the present invention are to provide a web handling apparatus which will supply a metal ribbon web to a metal rolling machine at a speed that produces quality parts efficiently; which has a dancer arm that will not create excessive slack or a force so great as to break the metal web; which has a dancer arm in association with a number of guide rollers to act as an accumulator; which includes a control system so that the speed of the handling drive motor is varied as the dancer arm deviates from the mid-point or normal operating position to provide uniform control of the drive motor throughout the movement of the dancer arm; and which is cost effective, utilizing fewer controls and one less motor.
In accordance with the invention, an accumulator apparatus comprises a dancer arm, a track roller assembly carried on one end of the arm and at least one vertical track for directing the track roller assembly in a substantially straight line vertical path. The accumulator apparatus also has a pivot on which the other end of the arm is attached, the other end of the arm is constructed so that there is relative movement of the arm axially with respect to the pivot.